National Center for Emerging and Zoonotic Infectious Diseases

Lessons Learned from Outbreaks:E. coli O157 Linked to Romaine Lettuce

Lyndsay Bottichio

Colin Schwensohn

Scott Nowicki

Adiam Tesfai

Natasha Dowell Central Regional MeetingMarch 6, 2019

2018 Outbreak of E. coli O157:H7 Infections Linked to Romaine Lettuce from the Yuma Growing Region

Day 1: Outbreak Detection

NJ Department of Health notifies CDC of a cluster of E. coli O157 infections in NJ and PA

– Most ill people reported eating salads from the same restaurant chain

CDC Foodborne Outbreak Response Team begins coordinating the investigation

Day 4: Confirming a Multistate Outbreak PulseNet confirms 8 O157:H7 illnesses from 6

states with the same PFGE pattern

Only common ingredient in the salads in NJ and PA appears to be romaine lettuce

– NJ collects records for romaine lettuce supplied to the restaurants

NJ releases a media statement about their investigation

Restaurant Chain A!!

A Break in the Case: Not Just Pre-Chopped Romaine?

State and local health officials in AK identified a cluster of illnesses at a correctional facility

– Ill people report eating romaine lettuce

Traceback investigations showed the lettuce was whole heads of romaine from Yuma, AZ region

Environmental Assessment Launched

Environmental assessment to determine possible routes of romaine contamination

– Observation and record collection

– Soil, water, and other sampling

Outbreak strain identified in irrigation canal water adjacent to many fields identified in traceback

– How did the outbreak strain get in the water?

– How did the water contaminate the romaine?

Romaine Exposures

152/179 (85%) reported romaine lettuce

20 illness sub-clusters, encompassing >50% of cases

– Includes restaurants, aforementioned AK correctional facility, and institutional cases in MN

– Sub-cluster in OH from chain fast food with no romaine

Epilogue

Outbreak declared over on June 28, 2018

– 21 day maximum shelf life for romaine

– 2-4 week reporting delay in PulseNet

240 ill people from 37 states

– 46% hospitalized; 28 people developed HUS; 5 deaths

People infected with the outbreak strain of E. coli O157:H7, by illness onset date

0

3

6

9

12

15

Outbreak Challenges

Challenges collecting epidemiologic data

– People who eat lettuce eat it often, and many have multiple exposures

– Many people don’t remember what type of lettuce eaten

Challenges interpreting traceback data

– Romaine from multiple farms/ranches/lots comingled at processing

– Common identifiers not always used to track through production/distribution

Challenges communicating clearly

– Labels on romaine lettuce do not typically list growing region

– Sometimes conflicting advice from various outlets and agencies

– Collateral damage to romaine producers outside of the Yuma growing region

Outbreak Conclusions

Largest multistate outbreak of E. coli O157:H7 infections in over a decade

Providing clear messaging was challenging; however, we needed to provide rapid advice to the public

– Outbreak grew quickly and was severe

Moving forward, how might we do things differently if this happens again?

– How can we use WGS going forward for this “clade of concern”?

Acknowledgments

State and local epi, lab, food safety, and agriculture partners

FDA

USDA

CDC Waterborne Team

CDC Enteric Lab

CDC FORT